The helicopter, a Pave Hawk assigned to the 48th Fighter Wing based at the air base RAF Lakenheath, was performing a low-level training mission along the Norfolk coast when it went down in marshland on Tuesday.

"Four airmen were killed in a U.S. Air Force HH-60G Pave Hawk helicopter crash at about 6 pm on Tuesday near Salthouse on the Norfolk coast," the 48th Fighter Wing said in a statement.

It said the names of the four men would be released 24 hours after their kin would be informed.

The Pave Hawk is made by Sikorsky Aircraft Co, a unit of United Technologies Corp.